1. Field of the Invention
The present invention relates to a anticollision device. It can be applied notably to the equipment of motor vehicles to enable them to avoid obstacles in front of them in the event of poor visibility for example. More generally, it can be applied to all functions relating to the prevention of collision between a moving object and an obstacle.
2. Description of the Prior Art
There are known anticollision systems for motor vehicles. A first known system uses a millimetrical radar whose antenna generally has a beam with an aperture equal to about 2 to 3 degrees. This width of the beam means that, at 100 meters from the vehicle, the width of the beam at -3 dB is about 5 meters and that, at 200 meters, its width is about 10 meters. With the latter width, an inoffensive lateral target, for example an indicator panel, may be illuminated by the beam and may therefore give rise to a false alarm. By contrast, at a small distance from the vehicle, the thinness of the beam means that an obstacle liable to collide with this vehicle may not be illuminated by the beam and may therefore be unobserved by the anticollision system. Finally, a heavy load in the rear of the vehicle or an uneven terrain may raise the end of the beam with respect to the obstacles in front of the vehicle and these obstacles then will not be illuminated.
To overcome these drawbacks, a scanning antenna could be used. However, such an approach is costly and therefore cannot be adapted to use on mass-produced vehicles.
There are known optical anticollision systems. They perform well in bright weather but are practically useless in poor weather, for example in rain or fog.
The aim of the invention is to overcome the above-mentioned drawbacks, notably by making it possible to obtain reliable and sure information relating to a risk of collision.